1. Field of the Invention
The invention relates to optical communication equipment and, more specifically but not exclusively, to the generation, transmission, and detection of an optical communication signal having two carrier frequencies, such as that suitable for optical phase-sensitive amplification.
2. Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention(s). Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
A phase-sensitive amplifier (PSA) provides optical-signal amplification while adding very little noise to the signal, with a noise figure of 0 dB (decibels) theoretically shown to be possible. A PSA is also a useful tool for regenerating optical signals and cleaning up signal distortions accumulated in the optical link. A PSA is compatible with various modulation formats and can produce optical gain over a relatively wide spectral range sufficient for WDM (wavelength-division multiplexing) applications. Optical transport systems that can realize in practice these and other benefits of phase-sensitive amplification are being currently developed.